This invention relates to a controlled exhaust system for low temperature enclosures such as a storage freezer and other enclosures held below freezing.
Enclosures to be held at low temperatures include a suitable freezing unit to lower the temperature. Commercially available freezer units use ammonia as the recircling heat exchange liquid. In large installations, such as cold storage rooms and warehouses for food, exhaust fan units are generally provided to exhaust the ammonia gaseous medium in the event of a break or leak in the recirculation system. Where the enclosure is to be held at or below a thirty-two degrees Fahrenheit (32.degree. F.), the exhaust fan units are suitably dampered with a temperature barrier to isolate the refrigerated room from the surroundings. Refrigerant leakage within the low temperature enclosure may however result in contamination and practical destruction of the stored food product. If the exhaust fan system rapidly and effectively removes the gaseous ammonia. Such contamination has been encountered for example, in a number of large low temperature food warehouses even though equipped with exhaust means.
Thus, there is a need for a means responsive to a refrigerant leak to more positively remove the contaminating refrigerant gases so as to protect the stored product, such as food.
The present inventor discovered that the contamination generally results because of an exhaust system malfunction created by the low temperature environment.